1. Technical Field
The present invention relates to a composite particle, a method for producing a composite particle, a powder core, a magnetic element, and a portable electronic device.
2. Related Art
Recently, the reduction in the size and weight of mobile devices such as notebook personal computers has become significant. Further, it has been planned to improve the performance of notebook personal computers to such an extent that they are equivalent to the performance of desktop personal computers.
In order to reduce the size and improve the performance of mobile devices in this manner, it is necessary to increase the frequency of a switching power supply. At present, the driving frequency of a switching power supply has been increased to about several hundred kilo hertz, however, accompanying this, it is necessary to also increase the driving frequency of a magnetic element such as a choke coil or an inductor which is built into a mobile device in response to the increase in frequency of the switching power supply.
For example, JP-A-2007-182594 discloses a ribbon composed of an amorphous alloy containing Fe, M (provided that M is at least one element selected from Ti, V, Zr, Nb, Mo, Hf, Ta, and W), Si, B, and C. It also discloses a magnetic core produced by laminating this ribbon and processing the resulting laminate by punching or the like. It is expected that with such a magnetic core, the AC magnetic properties are improved.
However, in the magnetic core produced from the ribbon, a significant increase in Joule loss due to an eddy current (an eddy current loss) may not be avoided in the case where the driving frequency of a magnetic element is further increased.
In order to solve such a problem, a powder core obtained by press-molding a mixture of a soft magnetic powder and a binding material (a binder) is used. In the powder core, a path in which an eddy current is generated is cut, and therefore, an attempt is made to reduce the eddy current loss.
Further, in the powder core, by binding the soft magnetic powder particles to one another with the binder, insulation is provided between the particles and the shape of the magnetic core is maintained. On the other hand, if the amount of the binder is too much, a decrease in the magnetic permeability of the powder core is inevitable.
Therefore, JP-A-2010-118486 proposes that such a problem is solved by using a mixed powder of an amorphous soft magnetic powder and a crystalline soft magnetic powder. That is, since an amorphous metal has a higher hardness than a crystalline metal, by subjecting a crystalline soft magnetic powder to plastic deformation when performing compression-molding, it is possible to improve the packing ratio and increase the magnetic permeability.
However, depending on the composition of the amorphous soft magnetic powder or the crystalline soft magnetic powder, the particle diameter thereof, or the like, the packing ratio sometimes cannot be sufficiently increased due to a problem of segregation of particles, uneven dispersion thereof, and the like.